1. Field of the Invention
The present invention generally relates to an optical communication apparatus and, more particularly, to an optical wiring connection structure of a signal or data transmission system used in an apparatus of an information.communication system which needs high-speed and large-capacity signal transmission.
The optical communication technology is widely used in a main communication system such as a long-distance transmission system since data can be transmitted at high speed by the optical communication technology. Especially, a technology called WDM (Wavelength Division Multiplexing) has been developed which transmits different information with a plurality of wavelengths through a single optical fiber simultaneously, and an information transmission with large capacity is realized.
A relay base in the main communication system station separates information sent by WDM into channel components of individual wavelengths, switches a destination of each channel component with a switch, and synthesizes a plurality of channel components into a single optical fiber signal on an individual destination basis. In order to perform such switching, it is necessary to switch a destination of an arbitrary channel component freely. More specifically, a cross connect function is necessary so as to output inputs of N channels as outputs of N channels.
In the future, in view of the progress in WDM technology, it is expected that it will be possible to send more than a hundred channel components through a single optical fiber. Therefore, there is a demand that the cross connect function have a capacity of handling more than a thousand channels.
2. Description of the Related Art
Such a multi-channel optical cross connect function may be achieved by a multistage optical switch such as that shown in FIG. 1.
Referring to FIG. 1, an optical fiber bundle 411 is made up of a group of optical fibers CH1 to CHM, which carry optical signal components of channels 1 through M demultiplexed from a WDM signal, respectively. Each of the optical fiber bundles 412 through 41N is configured by a group of optical fibers, which transfer optical signal components demultiplexed from another WDM signal, respectively. The optical fiber bundle 411 and the rest of optical fiber bundles are cross-connected at an optical cross connect part 43A. Each of the optical fiber bundles 411 through 41N has a corresponding optical connector switch 421 through 42N. The optical connector switches 421 through 42N are cross-connected with output side optical connector switches 441 through 44N at the optical cross connect part 43A.
In the structure shown in FIG. 1, the output side optical connector switches 441 through 44N are connected with the output side optical connector switches 451 through 45N in the next stage by an optical cross connect part 43B. Output side optical fibers bundles 461 through 46N extend from the respective optical connectors 451 through 45N.
The optical cross connect parts 43A and 43B can be realized by using a multitude of single-core optical fibers in the most simple way, as recited in Japanese Laid-Open Patent Application No. 06-31910. However, in such a structure, a very large space is needed so as to accommodate merely the optical fibers and optical connectors for each channel.
On the other hand, in Japanese Laid-Open Patent Application No. 11-178018, a structure is disclosed in which a board carrying an optical connector switch in the preceding stage and a board carrying an optical connector switch in the subsequent stage are orthogonal. In this way, by making the board of the preceding stage and the board of the subsequent stage cross at right angles, an arrangement of optical fibers at the optical cross connect parts 43A and 43B is simplified. However, even in such an optical connection structure, it is basically necessary to connect optical fibers one by one, thus workload is heavy and mistake-prone.
Additionally, in Japanese Laid-Open Patent Application No. 10-243424, a technology is disclosed in which a two-dimensional fiber array structured with N layers of optical fiber sheets each having M cores and a two-dimensional fiber array structured with M layers of optical fiber sheets each having N cores are crossed by orthogonal junction. According to such a structure, a compact cross construction can be realized. However, in order to prevent a coupling loss, it is necessary to stack the fiber sheets with a pitch accurately corresponding to the pitch between the cores. However, such a structure is difficult to manufacture.
Further, there is a method of using fiber sheet technology where optical fiber strands are laid along arbitrary lines and fixed by a resin or the like in a sheet-state. According to such a structure, since the optical fibers do not have protection films, a compact cross structure can be realized. However, as seen clearly from FIG. 1, optical fibers are concentrated and stacked at the center part of the cross structure. Optical fibers have tolerable minimum bending radiuses according to specifications. However, with such a structure, it is difficult to control a bending radius in a longitudinal direction caused by a pile of the optical fibers. For this reason, the performance characteristics of the optical fibers cannot be guaranteed.
It is a general object of the present invention to provide a novel and useful optical connection structure in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a compact and highly reliable optical wiring connection structure which can be easily manufactured.
The above-described object is achieved, according to one aspect of the present invention, by an optical wiring connection structure comprising a board that has a first end and a second end, a plurality of through-holes that continuously extend from the first end to the second end in the board, a plurality of optical wires each of which is provided in one of the through-holes, so as to extend continuously from the first end to the second end and an optical connector connected with each of the optical wires extending from the first end of the board.
The above-described object is also achieved, according to another aspect of the present invention, by an optical wiring connection structure comprising a first optical wiring connection part including a first board constituted by a plurality of substrates and having a first end and a second end, and a plurality of first through-holes continuously extending from the first end to the second end in each of a plurality of the first boards, a second optical wiring connection part including a second board constituted by a plurality of substrates and including a third end and a fourth end and positioned such that the third end connects with the second end of the first boards, a plurality of second through-holes continuously extending from the third end to the fourth end in each of a plurality of the second boards, a plurality of optical wires each of which is provided in a respective one of the first through-holes so as to extend from the first end to the second end, and further extend continuously in a respective one of the second through-holes corresponding to the first through-holes from the third end to the fourth end, a first optical connector that is provided to each of the substrates of the first board and connected with optical fibers extending from the first end and a second optical connector that is provided to each of the substrates of the second board and connected with second optical fibers extending from the fourth end, wherein the second board is positioned such that each board surface is orthogonal to each board surface of a plurality of the substrates of the first board, and the second board is provided such that each of the second through-holes corresponds to respective one of a plurality of the first through-holes exposed at the second end.
According to another aspect of the present invention, by using a board including through-holes as a first board, it is possible to change a pitch of the optical wires continuously from a first pitch corresponding to the optical connector to a second pitch corresponding to a thickness of the second board. Therefore, an optical cross connect using the optical wire is realized in the boundary surface between said second end and third end by stacking a multitude of said first boards so as to form a stacked material and to which stacked material connecting a stacked material which is structured by stacking the second boards. Such an optical wiring connection structure is sturdy, easy to manufacture and moreover, compact.
According to the present invention, an arbitrary three-dimensional optical wiring connection structure can be realized using optical fibers. The present invention is, since the optical fibers are held in grooves which function as guides, effective for preventing mistakes in laying the optical fibers. Additionally, since the optical fibers are protected in the grooves, it is possible to use optical fiber strands for optical wires. Therefore, the whole optical wiring connection structure can be further downsized compared to using optical fiber cables. Accordingly, the present invention has an advantage in providing an optical transmission of a large number of channels, for which especially downsizing is in great demand. Further, in the present invention, the optical fibers can be arranged according to a connector pitch so as to make connecting of the optical fibers easy.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the following drawings.